Orbital welding apparatus with safety interlock

ABSTRACT

An orbital welding apparatus includes a first housing defining a weld head assembly and a circular rotor disposed therein for rotation about a first axis. A welding electrode is carried by the rotor for welding. A second housing separate from the first housing forms a power transmission and has a second drive shaft extending therefrom. A flexible drive shaft connects the first drive shaft and the second drive shaft to conduct rotary drive forces from the first drive shaft to the second drive shaft while permitting the relative orientations of the first and second housings to be freely adjustable. A third and independent housing carries an electric drive motor and forms a power drive motor module with a rotary output shaft. A releasable clamping mechanism is provided for positioning and holding cylindrical members to be welded in an axially aligned relationship with their ends abutting in a single plane. A safety interlock mechanism is provided for sensing the releasable clamping mechanism in an operative position to prevent inadvertent operation or operation of the welding unit when the clamping mechanism is malaligned.

This application is a continuation-in-part of application Ser. No.07/606,421 filed Oct. 31, 1990, now U.S. Pat. No. 5,136,134.

BACKGROUND OF THE INVENTION

The subject invention is directed toward the art of welding and, moreparticularly, to an orbital welding apparatus for circular products suchas tubes or rods.

The invention is especially suited for incorporation in apparatus forwelding small diameter tubing in closely confined spaces and will bedescribed with references thereto. It should be appreciated, however,that the invention is capable of broader application and could be usedin many different welding devices of widely varying sizes for manypurposes.

Orbital arc welding equipment is often used to weld tubing and pipingfor use in fluid handling and processing system. Currently, there issignificant interest in welding small diameter tubing, fittings, andcontrol equipment such as valves, filters, and the like to form small,compact control and processing systems. Frequently, the variouscomponents must be welded in confined and nearly inaccessible areas. Inaddition, system designers are desirous of reducing, to the greatestextent possible, the size of the processing and control systems byreducing the distance between components. Much effort has been expendedin miniaturizing tube fittings and system components; however, the spacerequired by the welding apparatus has been a significant limitation onfurther system size reduction.

Safe use of potentially dangerous equipment has long been a concern inall areas of manufacturing and repair services. Fail-safe electricalinterlocks are one of the various methods of ensuring operator safetyduring use of such equipment. Generally, electrical interlocks have metwith great success and are therefore widely accepted in all areas ofmanufacturing and repair services.

The subject invention provides a unique combination of features whichallows welds to be made safely in extremely confined spaces and underconditions which have heretofore prevented use of orbital weldingequipment. The invention makes it possible to obtain the maximum systemsize reduction benefits through the use of miniaturized fittings andcomponents.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with one aspect of the invention there is provided anorbital welding apparatus which comprises a first housing defining aweld head assembly and including a circular rotor disposed therein forrotation about a first axis. A welding electrode is carried by the rotorand extends radially inward toward the first axis. Suitable drive gearsare carried in the first housing for rotating the rotor about the firstaxis and a first drive shaft is drivingly connected to the gears andextends from the first housing in a direction perpendicular to the firstaxis. A second housing separate from the first housing forms a powertransmission and has a second drive shaft extending therefrom. Aflexible drive shaft means connects the first drive shaft and the seconddrive shaft to conduct rotary drive forces from the first drive shaft tothe second drive shaft while permitting the relative orientations of thefirst and second housings to be freely adjustable. A third separate andindependent housing carries an electric drive motor and forms a powerdrive motor module with a rotary output shaft. Releasable connectingmeans are provided for quickly connecting the third housing with thesecond housing for permitting connection and disconnection of the rotaryoutput shaft of the motor module with the second drive shaft so that themotor module can be manually connected and disconnected from thetransmission and weld head assemblies quickly and easily.

The described arrangement permits the same motor module or power unit tobe quickly changed between weld heads intended for welding tubing ofdifferent sizes. Moreover, because the weld head is connected to thetransmission housing through a flexible drive, the motor module can havevarious desired orientations relative to the weld head module and theweld head module can be placed in extremely confined quarters withoutrequiring that the motor module be associated therewith in a particularorientation.

In accordance with a more limited aspect, there is a gas line extendingthrough the flexible drive shaft means to the housing to allow gas to besupplied to the weld head. Additionally, a gas supply connection extendsthrough the motor module housing. A valved connecting arrangement joinsthe gas line in the motor module with the gas line in the flexible driveshaft whenever a motor module is connected thereto. Preferably, thevalved connecting arrangement opens automatically when the motor moduleis connected to the flexible drive shaft.

In accordance with a further aspect of the invention, there areelectrical power cables and safety interlock wires also extendingthrough the flexible drive shaft. Suitable electrical connectors areprovided so that power and safety signal connection takes placeautomatically when the motor module is connected to the flexible driveshaft. Thus, when changing orbital weld head modules, there is anautomatic connection to the gas, the electric power and the safetyinterlock signal necessary for the operation of the weld head assembly.

The subject invention also provides an improved tube clamping assemblyfor use with the weld head to hold the cylindrical tube ends in axiallyaligned abutting relationship while the welding is performed to join thetube ends. The clamp assembly generally comprises a rectangular basewith an opening extending therethrough defining a path of movement forslidably receiving the orbital weld head. A first pair of transverselyspaced clamp arms extend from the base on opposite sides of the baseopening. A second pair of transversely spaced clamp arms extend from thebase on opposite sides of the opening in alignment with the first pairof clamp arms. The first and second pairs of arms include cooperatingclamp jaws for gripping on opposite sides of the tube ends andmaintaining them coaxially aligned with a first axis. The second pair ofarms are mounted for pivotal movement about a second axis which extendsparallel to the first axis and is in a common plane therewith which isaligned with the path of movement of the weld head into the opening inthe base member. Additionally, actuating means are provided for movingthe second pair of clamp arms between their open and closed positions.Further, in the closes position, the clamp arms mate along a line whichincludes the common plane.

The described arrangement of the arms opening in the manner describedallows the clamp assembly to be moved into position around tubesconfined in corners and closely adjacent walls since the movement of theclamping of the arms takes up a minimum amount of space and does notrequire any significant amount of space in the area beyond the outermostextent of the arms. That is, the clamp arms engage in the manner of apair of pliers being moved into position on the tubing. Access to theside of the tubing opposite the weld head is not required. Further, thedesign requires a minimum amount of space on the lateral sides of theclamp assembly.

A further aspect of the invention contemplates that the arms of theclamp assembly are moved between their open and closed position throughthe use of a cam actuating assembly wherein the assembly is located inan enclosed position between the arms and the base plate in a concealedand confined manner and wherein the operating portions of the actuatingmeans are located at a position spaced remotely from the outer end ofthe clamp assembly. Thus, when used in confined spaces, the actuatingmeans are readily operable even through the clamp elements are enclosedand confined by surrounding environmental structure.

In accordance with another aspect of the invention, the operatingportions of the clamp assembly actuating means are arranged such thatwhen the orbital weld head assembly is in operating position in theclamp assembly, interengaging portions prevent opening or operating ofthe clamp arms. Thus, the clamp arms cannot inadvertently open during awelding operation.

In accordance with a further limited aspect of the invention, there areprovided safety interlock wires extending through the flexible driveshaft means, which wires terminate at a transducer mounted to theorbital weld head assembly. The transducer is sensitive to therespective portions of the clamp assembly actuating means and the weldhead assembly being in said interengaging operating position to inhibitthe weld cycle when out of position.

As is apparent from the foregoing, a primary object of the invention isthe provision of an orbital welding apparatus which is capable of beingused safely in extremely confined spaces and which can weld extremelysmall fittings and produce miniaturized piping and control systems.

A further object of the invention is the provision of an orbital weldingapparatus of the general type described wherein the various modules usedto make up the system can be oriented at selectively differentarrangements relative to one another while the unit is being fitted tothe components being welded and while the apparatus in use and actuallymaking a weld.

A further object is the provision of a system of the type describedwherein the same power and control module can be used with a variety ofdifferent weld head modules so that the system is capable welding tubingof many different sizes while being operated off a single power module.

A further object of the invention is the provision of a system of thegeneral type described wherein a flexible drive connection conveysrotary power, electrical power, and weld environment gas simultaneouslyand wherein connection and disconnection of the power unit from the weldhead assembly automatically connects and disconnects not only the rotarypower but also the electrical power and weld environment gas.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangement ofparts, preferred and alternate embodiments of which will be described indetail in the specification and illustrated in the accompanying drawingswhich form a part hereof, and wherein:

FIG. 1 is a pictorial view showing the overall construction andarrangement of the orbital welding assembly of the subject invention;

FIGS. 2 and 2A are exploded pictorial views of the transmission andorbital weld head units, respectively, which together make up module Bof the assembly illustrated in FIG. 1;

FIG. 3 is an exploded pictorial view of the drive motor module A of theassembly illustrated in FIG. 1;

FIG. 4 is an exploded pictorial view of the tube clamping and holdingmodule C of the assembly illustrated in FIG. 1;

FIGS. 5-8 are partial side elevational views of the tube clamping andholding module, somewhat diagrammatic, showing the operation of theclamp arm actuating mechanism;

FIG. 9 is a cross-sectional view taken on line 9--9 of FIG. 1 andshowing the mounting and side loading arrangement for the electrodeholder;

FIGS. 10 and 10A are pictorial views in partial cross-sectionillustrating the manner in which the motor module is joined to thetransmission module;

FIG. 11 is an exploded partial pictorial view of the orbital weld headunit comprising module B of the assembly illustrated in FIG. 1;

FIGS. 12 and 12A are pictorial views showing the tube clamp and holdingmodule received on and removed from the welding head modulerespectively;

FIG. 13 is an electrical schematic representing the control logicexecuted by the weld head controller of the preferred embodiment; and,

FIG. 14 is a flow chart illustrating the control algorithm used in theweld head controller of the preferred embodiment to prevent inadvertentoperation of the orbital welding assembly with safety interlock of thesubject invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring more particularly to the drawings wherein the showings are forthe purpose of illustrating a preferred embodiment of the inventiononly, and not for the purpose of limiting same, FIG. 1 shows the overallconstruction and arrangement of an orbital welding assembly formedaccording to the subject invention and comprising a motor and drivemodule A which is arranged releasably connected to a transmission andwelding head module B which is associated with a tube clamp and holdingmodule C. Merely by way of explanation and general background, thevarious modules are arranged to be quickly and rapidly assembled anddisassembled so that, for example, the motor and drive module A can beused with different transmission and weld head modules B. For example, asingle motor and drive module can be used with a variety of differentsizes of transmission and weld head modules. Additionally, and forfurther example, the tube clamp and holding assembly C is quickly andeasily releasable from the transmission and welding head assembly B suchthat it can be separately connected to and positioned relative to thetubing to be joined and a multiple number of such tube clamping andholding units or modules can be used with a single transmission and weldhead module to allow welding to take place while additional tube endsare clamped in alignment by additional clamping and holding modules inpreparation for welding operation.

More specifically, and as best shown in FIG. 3, the motor and drivemodule comprises a relatively elongated housing assembly 10 formed by apair of clam shell type housing halves 12 and 14 (shown in FIG. 1) and atraverse end plate 16. The components 12, 14 and 16 are formed from anysuitable material such as a non-conductive thermoplastic or othernon-conductive material having adequate strength and wearcharacteristics. An elongated shell diameter electric motor 18 issupported within the housing by having its output end suitably connectedto the end plate 16. The drive shaft 20 of motor 18 extends freelythrough a suitable opening in the end plate 16 into a comparativelylarge diameter counterbored section 22. A drive connection element 24 ispinned or otherwise positively connected to the drive shaft 20 and hasan enlarged diameter end portion 26 which carries axially extending pins28. The pins 28 are retained in portion 26 and provide a rotary driveconnecting with the transmission and weld head module in a mannersubsequently to be described.

At the opposite end of the housing assembly 10 there is provided acentral inlet opening or passage 30 through which the electrical powerlines or cables 32 and 34 enter the motor drive housing. The cables 32and 34 are of sufficient gage to carry the maximum anticipated currentnecessary to effect a wide range of welding operations at the weldinghead module. In addition, a pair of lighter gage safety interlock wires31 and 33 pass through the central inlet opening or passage 30 en routeto a transducer mounted on the orbital weld head unit 52 discussedbelow. Similarly, a pair of medium gage electric motor control cables 35and 37 pass through the central inlet opening or passage 30 and aredirectly connected to the motor 18 within the housing assembly 10. Themotor control cables 35 and 37 may be fused at the motor 18 or mayprovide a fusible link between a power supply and the motor 18. In thepreferred embodiment, each of the above electrical conductors exit thehousing 10 through the opening 30 and in turn are received into a weldhead controller 300 described below.

Also entering through the opening 30 is a gas supply line 36 whichsupplies an inert gas to provide a suitable inert gas atmosphere aboutthe welding operation which takes place in the weld head module. Manydifferent types of gas are used to provide the necessary inertatmosphere and such are well known in the art.

The gas line 36 is connected to the head or end plate 16 and a flow line38 is provided through the head end for connection with the transmissionand weld head module. A check valve 39 is provided in flow line oropening 38 as shown in FIG. 10. In the preferred embodiment, the checkvalue 39 is a simple ball member 39a which is biased toward a seated,sealed position by a spring 39b. The ball member 39a is moved openagainst the bias of spring 39b when the motor and drive module A isjoined to the transmission and welding head module as will subsequentlybe described.

As also seen in FIG. 1, the power cables 32, 34 and the safety interlockwires 31, 33 are provided at their ends with electrical socketconnectors 40 and 41 respectively that, as will become apparent, allow asimple plug-in connection with the cooperating elements of thetransmission and weld head module in a manner which will subsequently bediscussed. The arrangement of the socket type connectors 40, 41 isconventional and they are suitably retained in the end plate 16 whilebeing insulated therefrom.

At the entrance end to the housing assembly 10, the power cables 32, 34,the safety interlock wires 31, 33, the motor control cables 35, 37 andthe gas line 36 are suitably enclosed by a resilient protective hosemember 29 which has its end clamped between the housing half sections 12and 14 (as shown in FIG. 1). Additionally, it should be noted that thehousing sections are releasably clamped together in any convenientmanner such as through the use of a plurality of socket head machinescrews 42 or the like.

Referring again to FIG. 1, it will be noted that the motor and drivemodule A is connected with the transmission and welding head module Bthrough the use of a conventional over center type, lever actuatedtoggle or latch mechanism indicated generally with the reference number46. The use of such latch mechanisms is well known and many differenttypes of quick release connections could equally well be used to allowpositive connection of these components while permitting readydisconnection when it is desired to change the particular weld headassembly being used with the motor and drive assembly or module A.

The Transmission and Weld Head Module Assembly B

Referring in particular to FIGS. 2 and 2A, the overall construction andarrangement of the components which make up the transmission and weldhead module are shown in some detail in exploded pictorial form. Ingeneral, the module B comprises a transmission unit 50 and an orbitalweld head unit 52. In the subject embodiment and in the preferred formof the invention, the transmission unit 50 and the weld head unit 52 aredrivingly interconnected by a flexible drive shaft assembly 54. However,in certain environments and under certain conditions of operation, theflexible drive shaft assembly 54 could be dispensed with and a directconnection provided between the noted components. In FIGS. 2 and 2A, theflexible drive shaft assembly 54 is shown as of indeterminate lengthwith opposite ends thereof shown connected to each of the components 50,52.

Referring more particularly to FIG. 2, it will be seen that thetransmission unit 50 includes a three-part housing including sideelements or housing components 56 and 58 (see FIG. 1), which arebasically mirror images of one another. The side elements 56 and 58cooperate to form a clam shell type housing which is interconnected in areleasable manner to the end plate member or wall 64 through the use ofa suitable mechanical fastener such as socket head machine screws 60.The outer configuration of the housing as formed by the components 56,58 has an overall size and external shape which generally corresponds tothe shape of the motor module unit. More particularly, it should benoted that when assembled as shown in FIG. 1, the outer end of the motormodule end plate 16 is closely received in the open end 62 of thehousing of a transmission unit 50. This provides a close coupling andsealing and encloses the electrical connections as well as the driveelements.

Positioned within the housing components 56, 58 and located inwardlyfrom the outer end 62 is the rigid end plate member 64 which is alsoreleasably connected to the housing components 56, 58 in any convenientmanner such as through the use of machine screws or the like (notshown). A counterbored section or opening 66 is formed in the end platemember 64 at the location shown. (See FIG. 10 also). Carried within thecounterbored section 66 and freely rotatable in suitable bearingslocated internally of the opening 66, is a gear-like drive element ormember 68. The external periphery of the larger diameter end of thedrive element 68 is provided with a multiplicity of uniformly spaced,generally semi-cylindrical recesses 70 which are sized and spaced so asto closely and drivingly engage the axially extending pins 28 on thedrive connection element 24 (see FIG. 3) when the units are in thecoupled condition shown in FIG. 1.

It should be noted that the opposite end of the housing component 56, aswell as housing component 58, including integral wall sections formed toprovide an outer end wall. The two housing components 56, 58 have matingsemi-cylindrical recesses which together define a cylindrical opening 72which is sized to closely receive the end 74 of the flexible drive shaftassembly 54. End 74 is a rigid metal collar and is clamped between thehousing components 56, 58 and held therein through cooperating groovesas illustrated.

The flexible drive shaft assembly 54 is a conventional flexible driveassembly. The outer housing or sheath 55 of this flexible drive assemblyis formed of a braided Teflon hose covered with a stainless steelbraided outer layer. Extending axially through the center of the outerhousing or sheath 55 is the flexible drive shaft element 76 whichterminates in a rigid drive connection or end 78. The space availablewithin the outer housing or sheath 55 is sized so as to be capable ofholding the electrical cables 32a, 34a and safety interlock wires 31a,33a. In the preferred embodiment illustrated, it is not necessary thatsheath 55 accommodate the motor control cables 35, 37 as they terminateat the motor 18 within the motor and drive module A.

However, as an alternative to the electrical connection scheme of thepreferred embodiment, the motor 18 and the safety interlock transducer101 discussed below may be series-connected. In this topology, the outerhousing or sheath 55 must be large enough to accommodate the electricalcables 32a , 34a and two wires sized according to the capacity of themotor control cables 35, 37. That is, in the alternative seriesconnection, a first motor control cable is connected directly from theweld head controller 300 to a first terminal of the motor 18 in thedrive module A. The second motor control cable is routed directly fromthe weld head controller 300 to a first contact of the safety interlocktransducer 101 at the welding head unit 52 through the transmission unit50 and the outer housing or sheath 55. To complete the circuit ofcourse, a motor control cable-sized wire must connect a second contactof the safety interlock transducer 101 at the welding head unit 52 tothe second terminal of the motor 18 in the drive module A.

Referring once again to the preferred embodiment, there is additionallysufficient space through the interior of the housing so as to allow freepassage of the gas line 36 connecting with opening 38 (as shown in FIG.3). In this regard, a suitable opening 80 is formed through the end wall64 at a location corresponding to opening 38 in the end wall 16 of themotor and drive module A. A suitable sealed connection is providedbetween openings 80, 38 by an O-ring 81 which is located in a recessabout opening 80 and engaged by boss 38a which extends out about opening38 as shown in FIGS. 10 and 10A. It should also be seen that the ends ofcables 32a and 34a are connected to suitable plug type electricalconnectors 82 and 84 respectively. Similarly, ends of the safetyinterlock wires 31a and 33a are connected to suitable plug typeelectrical connectors 81 and 83 respectively. Connectors 81-84 are ofconventional design, size and shape. The electrical connectors 82 and 84are suitably mounted in the end wall 64 at locations corresponding tothe locations of the socket connectors 40 of the motor module A.Similarly, the electrical connectors 81 and 83 are suitably mounted inthe well wall 64 at locations corresponding to the locations of thesocket connectors 41 of the motor module A.

The end 78 of the flexible drive shaft element 76 is connected to thedrive member 68 by a cooperating flat and a C-ring or spring clip. TheC-ring 86 and the flat 78a provide a rotary drive connection in whichthe shaft end 78 can axially move by sliding as is required when theflexible drive unit undergoes substantial bending. As can beappreciated, the overall arrangement thus far described allows rapidconnection and disconnection of the motor module from the transmissionunit 50. Additionally, as can be seen, the electrical and gasconnections are made automatically upon a simple plugging together ofthe two components.

The orbital weld head is, as previously mentioned, connected to theopposite end of the flexible drive shaft assembly 54. The details ofconstruction of the weld head are best illustrated in FIG. 2A. As showntherein the orbital weld head 52 generally comprises an outer frame andhousing 90 which is defined by a pair of opposed body sections ormembers 92 and 94. These sections are suitably molded or machined from anon-conductive, high strength, high temperature resistant material. Thebody sections 92, 94 are joined in mating relationship in any suitablemanner such as through the use of socket head machine screws 96. Itshould be seen that the body sections 92, 94 each include a firstgenerally rectangular end portion or body section 92a and 94arespectively. These sections cooperate to define an internal chamber ofgenerally rectangular shape into which a right angle drive assembly 96is releasably received. The details and arrangement of the driveassembly 96 will subsequently be described. For the present, however, itshould be noted that the body members 92 and 94 each further includerelatively thinner and smaller generally rectangular sections or members92b and 94b respectively. These sections are arranged to house thegearing and transmission members for connecting rotary motion from theright angle drive assembly 96 to the rotor or electrode holder 98. Inthis regard, FIG. 9 together with FIG. 2A shows the overall arrangementfor the electrode holder and the mounting thereof. More particularly,each of the sections 92b and 94b cooperate to define a tube receivingthrough opening 100 and a laterally open entrance area 102. Thisarrangement allows the tube ends to be positioned in abutment and theweld head moved laterally thereover to bring the abutted tube ends intoalignment with the electrode holder at the location necessary forperforming the weld. The tube ends are suitably held in proper alignmentand position by the tube holding and clamping assembly C in a mannersubsequently to be described.

As shown, the rotor or electrode holder 98 is generally circular inshape but has an open side or opening 103 which is of a width sufficientto allow the holder to pass over the exterior diameter of the particularsize of tubing which the weld head 52 is intended to weld. Both sides ofthe rotor or electrode holder 98 have a continuous convex configurationas illustrated to define circular guide surfaces 106, 108. In theembodiment under consideration, the electrode holder 98 is formed from arelatively hard copper; however, any suitable wear resistant andelectrically conductive material could be used. The body section 92b isprovided with an inwardly extending machined grooved 110 which isconcentric with the opening 100 and provides a guide track whichreceives the guide surface 106. In the body section 94b, there is acircular recess 112 which is coaxial with the housing 100 and ismachined to receive a circular brush member 114. The brush member 114has a circular shape with its upper surface shafted to form acomplementary guide track for the guide surface 108 on the rotor orelectrode holder 98. The surface is identified with the numeral 116 andextends circumferentially about the opening 100. The brush member 114 isconnected through an electrical bus bar 118 with a connector 120 whichis joined to the end of the power cable 34a (shown in FIG. 2). The powercable 32a (shown in FIG. 2) is electrically connected with a plugelement 122 which extends outwardly adjacent the sections 92b and 94b asillustrated in FIG. 2A. This completes an electrical circuit from cable32b to the tube holding and clamping module C in a manner subsequentlyto be described.

With reference now to FIG. 11, the body sections 92a and 94a are furtherprovided with suitable matching grooves 93a and 95a respectively forreceiving the safety interlock wires 31a and 33a while permitting thebody sections 92 and 94 to matingly engage as described above usingsocket head machine screws 96. The grooves 93a and 95a are inwardlyextending in a manner similar to groove 110 and recess 112. Of course,either one of the matching grooves may be dispensed with should it bedesired to machine only one of the body sections 92 or 94. However, aswould be understood from the FIGURE, if only a single groove is used,the overall dimension must be sufficient to receive the safety interlockwires 31a and 33a which may be single strands twisted together or anyother suitable two-wire configuration.

In addition to the grooves 93a and 95a, the body sections 92a and 94aare further provided with suitable matching recesses 97a and 99arespectively for receiving a safety interlock transducer 101 whilepermitting the body sections 92 and 94 to matingly engage as describedabove. The recesses 97a and 99a are inwardly extending in a mannersimilar to grooves 93a and 95a and are disposed in the respective bodyportions to permit direct electrical/mechanical connecting of leads ofthe transducer 101 to the appropriate safety interlock wires 31a and33a. Of course a single recess may be used if the transducer sizepermits. However, as described above, if only a single recess is used,the overall dimension must be sufficient to receive the entire safetyinterlock transducer 101 therein. The transducer may be a photo-sensor,a proximity switch or a simple mechanical micro-switch as will besubsequently described. In addition, the transducer may be provided witha raised portion circumferentially extending about the body thereof in amanner as to be matingly received in corresponding recesses in therespective recesses 97a and 99a. Other fastening schemes may similarlybe employed including the use of epoxies or the like.

As a result of the above described expedient, a complete electricalsafety interlock circuit is established from the weld head controller300 to the transducer in the welding head module B through the flexibledrive shaft assembly 54. The motor control cables 35 and 37 extend fromthe weld head controller 300 and into the motor and drive module A wherethey connect with the electric motor 18.

With reference once again to FIGS. 2 and 2A, the electrode holder 98carries a suitable tungsten electrode 126 which is adjustably clamped inthe holder by a set screw 128. As can be appreciated, rotation of theelectrode holder about the axis of opening 100 allows a weld to beperformed on abutting tube ends suitably positioned within the opening100 in a manner well known in the art.

The rotation of the electrode holder 98 is accomplished through a geartrain connected with the right angle drive assembly 96. In this regard,it should be noted that the outer periphery of the electrode holder 98is provided with gear teeth 130 which mate with corresponding teethcarried on the individual mating gears 132 and 134. Gears 132 and 134are positioned as shown and carried on suitable axles and bearingsmounted in the section 94b as illustrated. Drive gear 136 is in drivingengagement with the gears 132 and 134 to provide two separate drivetrains from the right angle drive unit 96. This allows drive to bemaintained even though the electrode holder 98 includes the opening 104.That is, the gears 132 and 134 are spaced apart a distance greater thanthe opening 104 so that one or the other of the gears is always incontact with the geared periphery of the electrode holder 98 at alltimes. The drive gear 136 is, of course, in driving engagement with theoutput gear 140 of the right angle drive assembly 96.

It should be noted that the right angle drive assembly 96 includes amachined block frame or housing element 142 which is preferably formedfrom a high strength thermoplastic and sized to be closely received andlocated by the recesses formed within the body sections 92a and 94a inthe manner illustrated. The output gear 140 is suitably carried on abearing and pin assembly which extends upwardly from the bottom of thehousing or frame element 142. A bevel gear element 144 is formedintegrally with the output gear 140 and mates with a corresponding bevelgear 146 mounted horizontally in a pair of bearings 148. The bearings148 are suitably received in an opening 151 formed at the right hand endof block 142. The drive lug from the flexible drive element 76 isreceived in the interior of the shaft joined to the bevel gear 146 andis connected therewith through the use of a C-ring 152. This connectingis also arranged to allow axial movement of the shaft portion 150relative to the bevel gear 146 to permit axial movement as requiredduring bending of the flexible drive cable 54. This connection is merelyflats formed on the sides of shaft portion 150 which slidably engage theC-ring 152. By forming the right angle drive unit as a separatecomponent with its own frame, maintenance, repair, and replacement ofthe drive is simplified.

The exterior housing of the flexible drive cable assembly 54 isconnected at its end through a metal sleeve or end portion 156 that isclamped between the body sections 92a and 94a and joined thereto througha socket head machine screw 158.

In addition, connecting means 152 is provided to provide section 92a.Connecting means 153 is hinged to body sections 92a with pin means 155.

The Tube Clamping and Holding Module C

The module C can best be understood by reference to FIG. 4 which showsthe module in somewhat of an exploded pictorial view. Broadly, the tubeclamping and holding module is designed so as to be of minimum sizecapable of performing the function to thereby allow it to be used inextremely tight cramped spaced and to assembly miniature tube fittingsin extremely compact small assemblies. The module is preferably formedfrom a high strength metal such as stainless steel and generallycomprises a first substantially rectangular base assembly 160 comprisinga pair of side members 162 which are joined by end members 164. The basedefines a rectangular opening 166 which is sized to closely but slidablyreceive members 92b and 94b of the weld head assembly 90. FIG. 1 showsthe weld head 90 and the fixture block module C in the assembledcondition. When in this assembled condition, the members 92b and 94bextend through the base assembly 160 such that the opening 100 islocated outwardly thereof or to the left as viewed in FIG. 4.Additionally, it should be understood that the base includes a blosswith an opening or socket to receive plug element 122 (see FIG. 2A) toassure a good electrical connection with electrical cable 32a. Inaddition, the base includes a pad 103 (FIGS. 12 and 12A) on the sideopposite the boss described above for communication of the presence ofthe clamping assembly properly received on the tube holding assembly. Inthe preferred embodiment, the pad 103 is a reflective surface foroperative communication with a photo-sensor variety safety interlocktransducer 101. Of course, other types transducers may be employedincluding micro-switches, magnetic proximity sensors or the like aswould be understood by those skilled in the art.

Associated with the base element 160 are a pair of outwardly extendingclamp arms 168 which are joined to the base or formed integrallytherewith to extend perpendicularly outward on opposite sides of theopening 166 to closely enclose the members 92b and 94bof the weld headassembly 90. In the embodiment under consideration, the pair of arms 168are rigidly positioned and interconnected by a cross piece 170.Associated with the first pair of arms 168 is a second pair of clamparms 172 which extend outwardly from the base assembly 160 in opposedaligned relationship with the first pair of rams 168. Each of the arms172 are mounted for independent pivotal movement relative to the arms168. The actual mounting and actuating mechanism will subsequently bedescribed; however, it should be noted that each arm of the first pairof arms, as well as each arm of the second pair of arms, carries a tubeclamp jaw 174. Although they could vary in construction, each of theclamp jaws 174 are identical and are of generally semi-circular shapeand define a semi-cylindrical clamp face 176. The individual jaws 174are provided with internal machined cuts 178 to produce resilient clampportions such that the clamp faces themselves can resiliently engage theperiphery of the tube ends being clamped. This design and the resilientnature of the clamp faces is the subject of a prior U.S. Pat. No.4,868,367 and a pending application commonly assigned, Ser. No. 373,029,filed Jun. 28, 1989 for "Collet Assembly for Cylindrical Workpieces"which are incorporated by reference herein. Each of the individual clampjaws is provided on its outer surface with a flange 180 which is engagedwith a corresponding counterbore 182 formed in the circular recess intowhich it is respectively received in the corresponding arm element.Preferably, the individual clamp jaws are welded or otherwise positivelyconnected in position in their respective clamp arms. It should be notedthat each of the jaws is located such that when the movable second setof clamp arms 172 is actuated to the closed position illustrated in FIG.1, the clamp jaws define spaced tube holding cylindrical sections whichare located closely adjacent and coaxial with the electrode holder 98 ofthe weld head assembly 90. Additionally, it is preferable that theindividual arms of the first and second sets of arms be provided withmeans to assure proper mating and alignment when they are in the tubeclamping or closed position illustrated. For this purpose, the arms 172are provided along their mating edge with a tongue element 184 which isarranged to be received within a corresponding groove 186 formed along amating edge of the first pair of arms 168. Thus, when the arms are inthe closed or tube clamping position, these cooperating tongues andgrooves assure proper alignment of the individual arms relative to theorbital weld head 90.

Of particular importance to the tube clamping and holding module C isthe manner in which the movable arms 172 are mounted and actuated. Asillustrated in FIG. 4, each of the arms 172 are independently mountedfor rotation about an axis 188 which extends transversely through theopening 166 and generally perpendicular to the path of insert movementof the weld head into the module C. This path of movement is illustratedgenerally by the arrow 190. Additionally, the two arms mate along aplane which includes the axis of opening 100 of the weld head module 90as well as the axis 188. It has been found that when the jaws can beopened in this manner, the weld head and tube clamp assembly are capableof being inserted into extremely confined areas and can make welds ontubes located in structural corners and other confined areas nototherwise weldable with typical prior art units.

Although the particular manner of mounting the movable arms 172 couldvary, in the subject embodiment a pair of shoulder screws 192 arereceived through suitable openings formed in the arms 172 and threadedlyengaged with the sides 162 of the base assembly 160. Each of the arms 17are independently actuated by a separate actuating means which takes theform in the subject embodiment of separate cam actuating assembly 194and 194a. These cam actuating assemblies are independently operable andmove the associated arm 172 independently between open and closedpositions. They are, however, mirror images of one another as can bereadily appreciated. For present purposes, a detailed description of theassembly 194 and its method of operation should be understood as equallyapplicable to assembly 194a subject to the understanding that 194a is amirror image of 194. Referring in particular to FIGS. 4-8, the operationof the operating or actuating assembly 194 can be understood.Specifically, as shown, the actuating assembly 194 includes a cam platemember 196 which is mounted for pivotal movement about a pine 198 whichis positioned such that the axis of rotation of the cam plate member 196is parallel to the axis 188. The cam plate is located in an enclosedposition between the lateral side 162 and the associated arm 172 as bestseen in FIG. 4. Each of the arms 172 includes a cam surface 200 which isinclined as best shown in FIG. 5. The cam surface 200 extendstransversely of the arm and is engaged by an outwardly extending camlobe 202 carried on plate member 196. Additionally, the overall shape ofplate member 196 is best illustrated in FIG. 5 and includes a laterallyextending handle portion or actuating member 204 which is accessiblefrom the ends of the module C. The cam plate 196 also carries a pin 205which extends outwardly through the arm 172. As best illustrated inFIGS. 4 and 5, the arm includes a somewhat L-shaped opening 206 intowhich the pin 205 and the outer end of pivot pin 198 can extend.

Referring more particularly to FIGS. 5-8, the overall operation of theactuating mechanism can best be understood. FIG. 5 shows the arm 172 inits tube clamping or closed position. In this position, the cam lobe 202is in somewhat of an over center position and the pin 205 is spaced fromthe sides of the L-shaped opening 206. If the actuating member 204 ispulled in the direction of the arrow shown i FIG. 6, the pin 205 engagesthe side of opening 206 as shown. With further movement in the directionof the arrow, the cam plate is rotated rotating the pin 205 to engagethe surface and drive the arm 172 in a counter-clockwise direction.Continued movement moves the arm to a full open non-clamping position asillustrated in FIG. 8. In this position, the spacing between the outerends of the arms 172 and the cooperating arms 168 are such as to allowthe jaws to be moved into and out of engagement with the tube ends whichare being welded or have just been welded.

When the cam plate member is actuated in the opposite direction, the camlobe 202 engages with the surface 200 and applies a closing force tomove the associated arm 172 back in a clockwise direction to a closeddirection as viewed in FIG. 5-8. It should be noted that throughout thismovement that a positive drive takes place and when in the FIG. 5position, the cam plate 196 is generally in a slightly over centerposition so that it tends to maintain its clamped position until it ismanually moved in the opening direction. It should be noted further thatduring the closing operation, the pin 205 does not act to move the arm172.

The safety interlock control logic will now be described with referenceto FIGS. 13 and 14. FIG. 13 illustrates the weld head controller 300executed in simple "ladder logic" diagram form comprising relays,pushbutton and a limit switch. In FIG. 13, the safety interlocktransducer 101 is represented schematically as a normally open doublepole signal throw limit switch LS1. A pushbutton PB on an operator panelof the weld head controller 300 momentarily energizes relay coil CR1when depressed by the operator. When the clamping assemble C is properlyreceived over the welding head B as described above and illustrated inFIG. 12, the transducer 101 produces a signal indicative of a safecondition. This is represented schematically in FIG. 13 as the closureof normally open limit switch LS1. When the clamping assemble C is notproperly received over the welding head B as described above orcompletely removed therefrom as illustrated in FIG. 12A, the transducer101 does not produce the safe signal. This is represented schematicallyin FIG. 13 as the normally open limit switch LS1 opened.

With the switch LS1 closed, actuation of the pushbutton PB energizes thecoil of relay CR1. This closes the contacts R₁₁ in turn energizing thecoil of relay CR2. Relay CR2 closes the contacts R₂₁, R₂ and R₂₃. It canbe seen that the contacts R₂₁ are used as a latch to maintain the coilof relay CR2 energized. Should the clamping assemble C move or otherwiseshift from a position of not being properly received over the weldinghead B as illustrated in FIG. 12A, the safe signal from the transducer101 will be removed. This is represented schematically in FIG. 13 as thelimit switch LS1 opening. When in an operating condition, the contactsR₂₂ and R₂₃ energize a motor control circuit MCC and a weld head controllogic circuit WCL respectively. The motor control circuit MCC may be asimple fixed voltage signal or a more sophisticate profile as may beprovided by a PLC, a computer numerical control or the like. The weldhead control logic circuit WCL may similarly be a PLC, a computernumerical control or the like. The motor control circuit MCC and theweld head control logic circuit WCL share a common proprietary controlplatform in the preferred embodiment.

The process for initiating a weld cycle is illustrated in FIG. 14. Theprocess may be executed in software on the weld head controller 300 orin any other arrangement such as in hardware or the like. In thepreferred embodiment, the method comrpises the steps of first reading acondition of the start pushbutton 502. If the button is actuated, thecontroller 300 inspects the transducer 101 to determine 504 the clampingassembly C as being properly received over the welding head B. If notproperly received, an error signal is generated 506 which may include avisual and/or audio signal to alert the operator. If the clampingassembly C is properly received over the welding head B, the weld cycleis initiated 510. Once initiated, monitoring of the position of theclamping assemble C is not longer necessary. In the event that theclamping assembly C is moved to an unseen position or the like 512, theweld cycle is immediately halted 514. That is, if the clamping assemblyC is detached from the welding head B, the current to the electrode 126is interrupted by virture of the physical separation of the components.An appropriate message or other signal is generated 516 to alert theoperator of this condition using various sensing means well known in theart. When the weld cycle completes 520, the control logic returns to anidle state 530 where the pushbutton is monitored. Of course, someprovisions may be made for resuming a welding cycle which may have beeninterrupted 514 as understood by one of ordinary skill in the art.

The invention has been described with reference to the preferrredembodiment. Obviously, modifications and alterations will occur toothers upon a reading and understanding of this specification. It isintended to include all such modifications and alterations insofar asthey come within the scope of the appended claims or the equivalentsthereof.

The invention having thus been described, I now claim:
 1. An orbitalwelding system comprising:a weld head controller; a first housingdefining a weld head and having and having a circular rotor disposedtherein for rotation about a first axis, a welding electrode carried bysaid rotor and extending radially inward toward said first axis, drivegears in said first housing for rotating said rotor about said firstaxis and a first drive shaft drivingly connected to said drive gears andextending from said first housing in a direction perpendicular to saidfirst axis; a second housing separate from said first housing and havinga second drive shaft extending therethrough; a flexible drive shaftmeans connecting said first drive shaft and said second drive shaft forconducting rotary drive forces from said second drive shaft to saidfirst drive shaft while permitting the relative orientations of saidfirst and second housings to be freely adjusted; a third housingconnected to the weld head controller and carrying an electric drivemotor having a rotary output shaft; a gas flow line and electric powercables extending through said second and third housings for supplyinggas and electric power to said first housing; connecting means forpermitting rapid selective connection and disconnection of said thirdhousing with said second housing and while simultaneously connecting anddisconnecting said output shaft and said second drive shaft and said gaslines and said power cables in said second and third housing; a tubeclamp assembly slidably received by said first housing for holding acylindrical tube within said circular rotor at a location concentricwith said first axis; signal generating means for generating a firstsignal when said tube clamp assembly is slidably received by said firsthousing; and, means in said weld head controller for selectivelyproviding said gas and electric power to said gas flow line and electricpower cables in response to said first signal.
 2. An orbital weldingapparatus as defined in claim 1 wherein said signal generating meanscomprises a transducer disposed on said weld head.
 3. An orbital weldingapparatus as defined in claim 2 wherein said transducer is an electronicreflective photo-sensor and wherein said tube clamp assembly is adaptedfor photo-reflective communication with said transducer.
 4. An orbitalwelding apparatus as defined in claim 2 including a gas flow lineextending from said second housing through said flexible drive shaftmeans to said first housing for supplying gas to said weld head.
 5. Anorbital welding apparatus as defined in claim 2 wherein said drive gearsinclude gears carried in a gear support frame which is removable as aunit from said first housing.
 6. An orbital welding apparatus as definedin claim 2 wherein said electrical power cables in said second housingextend through said flexible drive shaft means to said first housing. 7.An orbital welding apparatus as defined in claim 2 wherein saidconnecting means includes axially engagable plug members for connectingand disconnecting said power cables.
 8. An orbital welding apparatus asdefined in claim 2 wherein said connecting means includes manuallyoperable latch members.
 9. An orbital welding apparatus as defined inclaim 2 wherein said connecting means includes an axially engagabledrive connection between said output shaft and said second drive shaft.10. An orbital welding apparatus as defined in claim 2 wherein saidclamp assembly includes cooperating clamp jaws mounted for pivotalmovement about an axial parallel with said first axis and generallyperpendicularly aligned with said first drive shaft.
 11. For use in anorbital welding apparatus, a tube clamping assembly for holdingcylindrical tube ends in axially aligned abutting relationship whilewelding is performed by an orbital weld head of the orbital weldingapparatus, said clamping assembly including:a generally rectangular basewith an opening extending therethrough for receiving the orbital weldhead; a first surface adapted for selective communication with aposition transducer on said weld head when received in said base; afirst pair of transversely spaced clamp arms extending from said base onopposite sides of said opening; a second pair of transversely spacedclamp arms extending from said base on opposite sides of said opening inalignment with said first pair of clamp arms; said first and secondpairs of clamp arms including cooperating clamp jaws for gripping onopposite sides of the tube ends to be welded and maintaining themcoaxially aligned with a first axis; pivot means mounting said secondpair of arms for pivotal movement in a first direction about a secondaxis parallel to said first axis to move the clamp jaws in a firstdirection to a tube end gripping position; the arms in said second pairof arms each having a cam plate member associated therewith andpositioned between the base and the respective arm for moving saidrespective arm about said second axis, each cam plate member mounted forindependent pivotal movement about a third axis parallel to said firstaxis; and said first and second axes being in a common plane which isgenerally perpendicular to said base.
 12. The tube clamping assembly asdefined in claim 11 wherein said first surface comprises a smoothmetallic land area adapted for selective magnetic communication with aproximity sensor on said weld head when received in said base.
 13. Thetube clamping assembly as defined in claim 11 wherein said first surfacecomprises a highly-reflective land area adapted for selectiveopto-reflective communication with a reflective photo sensor on saidweld head when received in said base.
 14. An orbital welding apparatusfor welding abutting ends of cylindrical members comprising:an orbitalwelding head including a housing with an electrode holder means havingan electrode mounted therein for rotation in a first plane about a firstaxis; a clamping assembly for positioning and holding the cylindricalmembers to be welded in an axially aligned relationship their endsabutting in a single plane; releasably connecting means for connectingsaid housing to said clamping assembly when said housing is in anoperative position; means on said orbital welding head for selectivelygenerating an electrical signal when said housing is connected to saidclamping assembly; and means for energizing said electrode to initiate aweld responsive to said electrical signal and for preventingenergization of said electrode when said housing is not in saidoperative position.
 15. An orbital welding apparatus for weldingabutting ends of cylindrical members comprising:a tube holding assemblyfor positioning and holding the cylindrical tubes to be welded in analigned position; a first housing defining a weld head adapted forselectively receiving said tube holding assembly and having a circularrotor disposed therein for rotation about a first axis, a weldingelectrode carried by said rotor and extending radially inward towardsaid first axis, drive gears in said first housing for rotating saidrotor about said first axis, a drive shaft drivingly connected to saidgears and means for generating an electrical signal when said tubeholding assembly is selectively received on said first housing; aseparate housing carrying an electric drive motor having a rotary outputshaft; each said first and separate housings carrying a gas flow lineand electric power cables for supplying gas and electric power to saidweld head; each said first and separate housings carrying a safetyinterlock wires from an orbital welding apparatus controller to saidelectrical signal generating means in said weld head; connecting meansfor permitting selective manual connection and disconnection of saidfirst and separate housings, said connecting means including means forproducing simultaneous connection and disconnection of said drive shaftand said rotary output shaft while simulatenously connecting anddisconnecting said gas lines and said power cables in said first andseparate housings; and a flexible drive shaft drivingly connectedbetween said drive shaft and said gears with said flexible drive shaftand said power cable and said gas lines extending through a commonflexible housing.
 16. A method of operating an orbital welding apparatusfor welding abutting ends of cylindrical members comprising the stepsof:providing an orbital welding head including a housing with anelectrode holder means having an electrode mounted therein for rotationin a first plane about a first axis; providing a clamping assemble forconnection with said housing and for holding the cylindrical members tobe welded in an axially aligned relationship connecting said clampingassembly to said housing when said housing is in an operative position;positioning and holding the cylindrical members to be welded in theclamping assembly and in said axially aligned relationship with ends ofthe cylindrical members abutting in a single plane; selectivelygenerating an electrical signal when said housing is connected to saidclamping assembly; and, energizing said electrode to initiate a weldresponsive to said electrical signal and preventing energization of saidelectrode when said housing is not in said operative position.